Chapter 3: Stoichiometry and Chemical Calculations

Vocabulary practice flashcards covering fundamental stoichiometry concepts, significant figures, molar mass, chemical equations, limiting reagents, theoretical and percent yield, and empirical and molecular formulas.

Leading Zeros

Zeros that appear before all non-zero digits in a number; according to significant figure rules, they are not significant.

Interior Zeros

Zeros located between non-zero digits; according to significant figure rules, they are always significant.

Trailing Zeros

Zeros placed at the end of a number; according to significant figure rules, they are significant.

Significant Figures Addition and Subtraction Rule

The rule stating that the final calculated answer must be as precise as the least accurate number (retaining the fewest decimal places).

Significant Figures Multiplication and Division Rule

The rule stating that the final calculated answer must have the same number of significant figures as the measurement with the least number of significant figures.

Mole

A unit defined as the number of atoms present in exactly $12\,\text{g}$ of carbon-12 ($^{12}\text{C}$), equal to $6.0221 \times 10^{23}$ atoms, molecules, or objects.

Avogadro's Constant ($N_A$)

The proportionality constant equal to $6.0221 \times 10^{23}\,\text{mol}^{-1}$ representing the number of particles (atoms, molecules, or objects) contained in one mole of a substance.

Molar Mass ($M$)

The mass of one mole of objects or particles of a substance, calculated by the formula $M = \frac{m}{n}$, where $m$ is mass and $n$ is the amount in moles.

Average Atomic Mass

The sum of the masses of an atom's isotopes, each multiplied by its natural abundance: $\text{avg atomic mass} = (\text{fraction isotope 1})(M_{\text{isotope 1}}) + (\text{fraction isotope 2})(M_{\text{isotope 2}}) + \dots$

Chemical Reaction

A process in which one or more substances are converted into another substance.

Skeleton Equation

An initial, unbalanced chemical equation that shows the chemical formulas of the reactants and products before coefficients are adjusted.

Reaction Stoichiometry

The relationship between the amounts of reactants consumed and products formed in chemical reactions, as expressed by the coefficients of a balanced chemical equation.

Limiting Reagent

The reactant that governs and limits the maximum amount of product that can form because it is completely consumed first.

Theoretical Yield

The maximum quantity (amount, mass, or volume) of product that can be obtained from a given quantity of a specified reactant based on stoichiometric calculations.

Percent Yield

The fraction of the theoretical yield that is actually produced, expressed as: $\text{percent yield} = \left(\frac{\text{actual yield}}{\text{theoretical yield}}\right) \times 100\%$

Mass Percent Composition

An intrinsic property expressing the mass of an element as a percentage of the total mass of the sample or compound: $\text{mass } \% = \left(\frac{m_{\text{element in sample}}}{m_{\text{total}}}\right) \times 100\%$

Empirical Formula

A chemical formula expressing the simplest whole-number ratio of the moles of each element present in a compound.

Molecular Formula

A chemical formula that indicates the actual number of atoms of each element in a molecule, determined by the ratio of the molar mass of the compound to its empirical formula mass.